It focuses on one of the most depressing and profoundly violent chapters in human history. It makes ZERO effort to be historically accurate or have anyone look or sound like the person they are playing. The entire movie is filled with brutal executions, horrible crimes against children, and portrayals of the most sociopathic and soulless people to ever exist. It's perfect.
The comedy is very reminiscent of the Cohen Brothers or Christopher Guest. There isn't a single joke but it's hilarious. I love how the movie uses various English dialects to portray the linguistic and cultural diversity of the Soviet Union instead of forcing clunky Slavic accents. It doesn't care at all and it comes off as flawless.